1. Field of the Invention
The present invention relates generally to a procedure known as electrophoresis and, more particularly, the present invention is directed to a protective container for an electrophoretic media of the type referred to as an electrophoretic gel. The container supports the electrophoretic gel from the time of manufacture to the time of use. The container provides support for the gel as the electrophoretic gel is transported from one location to another, and when the electrophoretic gel is being stored.
2. Description of the Prior Art
Electrophoresis involves the placing of a sample substance, such as blood serum or urine, in a support medium. A direct current electrical potential is maintained across the support medium through the use of opposed electrodes. Support media characteristically include paper, agar, agarose, cellulose acetate and polyacrylamide. The electrical potential causes the colloidal particles in the sample substance to migrate toward one or the other electrodes. The amount of migration is determined by the electrical charges on the particles in the sample substance and the magnitude of the electrical potential. Particles with similar properties tend to migrate or group into defined areas and thus a determination may be made as to the amount of each class of substance present in sample.
It is important to the electrophoretic process that the support medium be uniform and free from imperfections. Agarose has been found to be an excellent support medium. The agarose is formed into a gel layer into which the sample substance is placed. An electrical potential is maintained across the gel layer and particle migration takes place. The gel layer may then be reacted with a chemical mixture or reagent to render the separation visible and readable by a trained technician. Different chemical mixtures may be employed to visualize different classes of separated substances.
When gel layers are to be used commercially, such as in clinical laboratories, the gel layers must be transported or shipped from the place of manufacture to the clinical laboratory and the gel layers must be stored until they are to be used. Heretofore, problem have occurred both in the shipping and in the storing of gel layers. The problems are twofold: physical damage to the gel layers and dehydration of the gel layers. Although the gel layers are usually adhered to a support substrate, and placed in containers, both damage to the gel layer and dehydration of the gel layer may still occur. The containers heretofore used normally take one of two forms: either separate top and bottom pieces which are to be secured together or top and bottom pieces which are hinged together and which are opened or closed. Containers are made of substantially rigid plastic such as styrene.
One approach to the protection of the gel layer is disclosed in U.S. Pat. No. 4,314,897 to Monte et al wherein the top and bottom portions of a container physically trap the upper and lower surfaces of the substrate onto which the gel layer is adhered. This precludes movement of the substrate thus tending to reduce damage to the gel. The sealing relationship between the container top and bottom also tends to reduce dehydration of the gel.
Another approach is illustrated in U.S. Pat. No. 4,709,810 to Mayes, assigned to the assignee of the present invention, wherein the substrate is maintained within closed, sealed container portions by water adhesion. The water adhesion tends to protect the gel layer from movement and the sealing of the container portions tends to reduce dehydration. Other prior art techniques include the provision of alignment apertures in the substrate and alignment pins in the container such that when the substrate (containing the gel layer) is placed within the container, the alignment pins of the container extend upwardly through the alignment apertures in the substrate to reduce lateral movement of the substrate. Alternate approaches are also illustrated in U.S. Pat. Nos. 4,741,814 and 4,759,838 both assigned to the assignee of the present invention.
Notwithstanding these prior art techniques, it has been found that the gel layer still tends to become damaged during shipment and storage primarily for two reasons. A first reason is that when a plurality of containers are shipped from one location to another, the containers are frequently rotated 90.degree. onto one side or even rotated 180.degree. and thus inverted, causing the substrate to move free of the alignment pins. Furthermore, when a plurality of containers are shipped or stored, the collective weight of the containers tends to damage some of the containers and the gel layer within one or more of the containers.